The present invention relates to an electric type swash plate compressor for use in a vehicle air conditioner and the like.
An electric compressor is known as a compressor included in a refrigerant circulation circuit of a heat exchanger such as the vehicle air conditioner. In general, the electric compressor has an electric motor and a compression mechanism to compress refrigerant driven by the motor within an outer casing of the compressor. The compression mechanism is composed of pistons accommodated so as to reciprocate in cylinder bores in the compressor, and of a swash plate, which is located in a crank chamber defined in the compressor and converts rotating movement of the motor to reciprocating movement of the pistons. As for the motor, capacity to rotate at a high speed and a driving force to endure a high load torque are expected. So, the compressor needs to have a powerful motor. In the arrangement of the powerful motor against a high load for rotation, however, the temperature around the motor rises since the motor generates heat. The rise in the temperature around the motor heats the motor further, and that makes magnetic force of the motor decrease, and the compressor involves the risk that rotating efficiency of the motor falls. Therefore, it needs to cool down the motor to prevent the motor from rising in temperature.
When the swash plate rotates at a high speed, its temperature rises because of a sliding friction with a pair of shoes placed between the swash plate and the piston. Therefore, it also needs to cool down the swash plate to improve durability and sliding stability thereof.
As an arrangement to cool down the motor, Japanese Unexamined Patent Publication No. 7-133779 is known. In the arrangement, the discharged refrigerant from the compression mechanism, which is sent to the device downstream to the compressor, such as a condenser, is introduced into a motor chamber, and is used to cool down the motor.
In addition, Japanese Unexamined Patent Publication No. 9-236092 discloses the following arrangement. The refrigerant which is drawn into the compressor from the device upstream to the compressor, such as an evaporator, is used to cool down the motor.
However, in the former arrangement, the discharged refrigerant used to cool the motor is high in pressure and in temperature since the refrigerant is compressed. Therefore, the following two problems are caused when the refrigerant in the above state is used to cool down the motor.
First, the discharged refrigerant in high pressure prevents the casing from making it compact and reducing its weight. That is, the motor chamber occupies a large space in the compressor, and it needs to improve the strength of the casing, such as an increase of the thickness of the casing, an increase of reinforcement and the thickness inside the casing, so that the casing can resist high pressure.
Second, the refrigerant used to cool down the motor in itself is high in temperature, so the motor is not efficiently cooled down.
In the meantime, both publications do not disclose that the refrigerant cools down the swash plate, but only disclose that the refrigerant is introduced into the motor chamber to cool down the motor. That is, it is not considered to cope with overheat of the swash plate under the present conditions.
The object of the present invention is to offer an electric type swash plate compressor which can be not only compact and reduced in weight but also efficiently cool down a motor chamber and a crank chamber.
To solve the above problems, the present invention has following features. The compressor has a motor chamber, a crank chamber and cylinder bores formed within an outer casing, and pistons accommodated in the cylinder bores so as to be reciprocated, and a drive shaft extended in the motor chamber and the crank chamber so as to be rotatably supported in the casing, connected to an electric motor in the motor chamber and reciprocating the pistons through the swash plate connected to the drive shaft in the crank chamber. A communication route, which introduces a refrigerant in lower temperature than a refrigerant in a discharge chamber into the motor chamber formed in an inner refrigerant circuit in the casing passes through the crank chamber.
According to the present invention, the motor chamber and the crank chamber of the electric type swash plate compressor are cooled down when the refrigerant in the inner refrigerant circuit in the casing is introduced through the communication route. The refrigerant introduced into both chambers is lower in temperature and in pressure than the refrigerant in the discharge chamber communicating with the external refrigerant circuit, or the discharge refrigerant. So, it can reduce temperature and pressure more in both chambers than the arrangement that the discharge refrigerant is used to cool down the chambers. That is, the cooling efficiency can be improved and moreover, the pressure resisting strength of the casing can be reduced.
Furthermore, the present invention has following features. The compressor is a multistage type having a first cylinder bore, where the refrigerant drawn from the external refrigerant circuit is compressed, and a second cylinder bore, where the refrigerant in intermediate pressure, at least once being compressed, is drawn and compressed. The communication route communicates an intermediate pressure chamber having the refrigerant in intermediate pressure with the motor chamber.
According to the present invention, the motor chamber and the crank chamber are cooled down by the refrigerant in the intermediate pressure discharged into the intermediate pressure chamber of the multistage compressor. Since the refrigerant in the intermediate pressure is much lower in temperature and in pressure than the discharge refrigerant, it is suitable for the improvement of the cooling efficiency and the reduction of the pressure resisting strength of the casing.
Furthermore, the present invention has following features. The motor chamber is arranged upstream to the crank chamber in the communication route, and at least a part of the refrigerant is introduced into the crank chamber through the motor chamber.
According to the present invention, before the crank chamber is cooled down, the motor chamber is cooled down. That is, the refrigerant in low temperature of which temperature does not rise in the crank chamber at least cools down the motor chamber, so the cooling efficiency of the motor chamber is further improved.
Furthermore, the present invention has following features. The communication route communicates either of the suction chamber having the refrigerant drawn from the external refrigerant circuit and the intake port introducing the refrigerant into the suction chamber with the motor chamber.
According to the present invention, the refrigerant drawn from the external refrigerant circuit is introduced into the motor chamber and the crank chamber. The refrigerant is still lower in temperature and in pressure than the refrigerant in intermediate pressure. Accordingly, the present invention is further suitable for the improvement of the cooling efficiency and the reduction of the pressure resisting strength of the casing.
Furthermore, the present invention has following features. The branch communicating passage, which is branched from the suction chamber or the intake port, constitutes the inner refrigerant circuit in the casing of the compressor and is arranged upstream to the motor chamber and the crank chamber.
According to the present invention, the suction refrigerant is introduced into the motor chamber and the crank chamber through the branch communicating passage. At that time some part of the suction refrigerant is introduced into both chambers, while the other part of the refrigerant is not introduced into both chambers but is drawn into the cylinder bores. Accordingly, the suction refrigerant, of which temperature highly rises in both chambers, occupies only a part of the refrigerant, so the refrigerant drawn into the cylinder bores does not rise in temperature relatively. That is, the fall of the compressive efficiency, which is caused by the increase of the specific volume by a rise of the refrigerant in temperature drawn into the cylinder bores, can be prevented.